Small Package, Big Surprise: 600+ HP from a 340

What do you call a small-block 340 that can develop 602 hp at 7,000 rpm on 91-octane go-go juice? Impressive comes to mind.

The idea for this project was to put together a streetable package by replacing a tired small-block with something to really brag about. The goal was to make 2 hp per cubic inch with a normally-aspirated motor on 91-octane pump gas. As far as we know, this engine combination has never been built before, so Mike Johnson of JMS Racing Engines in Monrovia, California, set out to do just that for customer John Copeland.

The new Chrysler R3, 340ci block and W-9 Chrysler heads (the heads used in Winston Cup and on Sprint Car engines) were purchased from Lawrence Roundtree at Mopartsracing.com. Because this combination is new, there were more than a few glitches to overcome in developing the package. Although 90 percent of this motor is available in the Mopar Performance catalog, when you're breaking new ground, some parts are not available, and no one knows how it will all fit together. This is where JMS's experience proved invaluable.

It's All in the Angle

Chrysler developed the R3 block because, traditionally, their blocks have 59-degree lifter angles, making it difficult for a high-rpm valvetrain to survive. The R3 block has the lifters at a 48-degree angle, giving a better pushrod angle. To begin with, our block (PN P4876672AB) was completely blueprinted. JMS drilled the oil galleys in the lifter holes because there were none there. Chrysler sells a jig to properly handle this task, but we're not sure why they don't drill them at the factory.

JMS also drilled oil drain holes at the top of the engine block, in the valley area, because without them, the oil would have to travel over a 1/2-inch-tall wall to reach the existing holes before it could drain back to the oil pan. This could effectively leave a quart of oil suspended up there at all times.

Because Chrysler moved the intake ports on the W-9 head to get the pushrod alignment straight, offset lifters needed to be used. JMS used a combination of centered, left, and right offset lifters. Neither Chrysler nor Comp Cams could clearly state what lifters were needed for this combination, but when it did come time for lifters, Comp was the only company that had offset lifters in a Mopar diameter. Each lifter had to be checked individually for geometry to see what offset was needed. Once the correct lifter offset was established, Comp Cams had to figure out what tie-bars were needed to connect the lifters. "Chrysler didn't know what lifters to use," said Mike. "They were on the phone with us asking what we came up with. That is why this motor is so cool. It's so new that even Chrysler is interested in what it took to put it together." The combination of lifters consisted of eight Comp Cams centered lifters (892C-1), four of the left offset lifters (892L-1), and four of the right offset lifters (892R-1). Eight Comp Cams link bars (CC814) hold the lifters together.

Getting to the Bottom

The forged 318, six-bolt flange crankshaft (PN P5249135) has a 3.31-inch stroke and 318/340 mains. Custom made Ross pistons were connected to Eagle 6.123-inch rods (356-CRS6123C3D). Working with Comp Cams, Mike calculated the custom grind camshaft (20-999-3) profile to be .631/.631-inch lift, with a .260/.260-degree duration at .050 on a 108 lobe center. The valvesprings were Isky (PN 9385) with matching titanium retainers and 10-degree locks. "You have to run a roller cam because of the offset lifters," Mike said. "You cannot buy an offset flat-tappet lifter. There are enough small roller cams available to make it streetable. This one may not be a grocery getter, but it is streetable."

The new W-9 aluminum cylinder heads (PN P5007066) only needed minor port work. Mike just knocked off the flashings and shined up the ports; there was no extensive work done. The heads, which feature a 50cc combustion chamber, were that good right from the factory. Manley custom-made the valves with 2.100-inch intake and 1.600-inch exhaust. The rocker setup is made by T&D for Mopar Performance. The pro race rocker-arm assembly (PN P5007470) was preset and included the shafts and bolts. The pushrod length had to be calculated. Manley supplies them off the shelf in increments of 0.050 inch over stock.

The high-rise intake manifold (PN P4582599) from Mopar is the only one available for W-9 heads with a 9.200-inch deck. For some reason, the intake and the heads didn't line up. Mike had to make 1/4-inch spacers to fit under each leg of the intake so the single-plane manifold would mate up to the heads correctly. We are told that little problem has since been corrected. Sitting on top of the manifold is a Barry Grant Gold Claw 850-cfm four-barrel carburetor. All told, the engine has a powerband of 3,600 to 8,500 rpm and idles at 850 rpm, which is incredible.

Special Challenges

Mike detailed some of the challenges encountered during the build. "We had to make a custom galley tray underneath the intake manifold because it was not yet available," he said. "The valvetrain became a real chore, as did the intake-manifold fitment. Even the front cover had to be machined to fit. We were a year too early building this motor. Chrysler asked us why things did not fit, and then they remachined it. Because of the feedback we gave them, parts are now becoming available.

"We had to make the thermostat housing and form water-return lines out of steel braided hose to fit under the intake manifold. The valve covers were not milled correctly, so we machined them straight for clearance so the hold-down nuts would fit. The valve covers also had to be milled around the valvesprings for clearance. We also had to cut the valve-cover gasket around the valvesprings so they would not hit. The heads had to be milled in the area of the inner head bolts in order to get them to fit. We also had to machine the balancer to make it fit on the front of the block."

Some parts were readily available from either Chrysler or the aftermarket. The harmonic balancer, Milodon oil pan (PN 30935), and the oil pickup were easily attainable. The timing chain and gears were standard, and the timing-chain cover (PN P4876632) was a racing piece. Headers will have to be custom-made for the car in which the engine will be installed.

Thrash it, Baby

We asked Mike if he was surprised at how the engine performed on the dyno considering the glitches he encountered while building the engine.

"Yes," he answered, "we had no problems at all during the two days we spent on the dyno. We put it on the dyno and just tuned it. We jetted the carburetor and played with the timing. It only took 34 degrees of total timing because the combustion- chamber size is very efficient. This combination is maxed out on power. I don't think more or less cam would help at all. We spent a lot of time in cam selection; it was not just a shot in the dark. I was on the phone with Comp Cams about it. They were the only ones in the industry who knew what I wanted in a 48-degree lifter. They were very helpful."

This project was difficult only because Mike was breaking new ground. The new W-9 heads were the issue, but they do make some awesome power. Now that he's done, Mike is going to disassemble the motor, go to 13.5:1 on the compression, and cam it up to see if he can get 700 horses out of 340 inches. There is also an R3 block with a 9.56-inch deck available. That's how you get the big-inch small-blocks like 450 ci with the W-9 heads. Everyone wants to see what he can get with that combination. Can we all say glutton for punishment?

"This thing is stout!" exclaimed Mike. "The amount of torque we found was impressive." He's been building high-performance engines for over 30 years and was surprised at the 496 ft-lb of torque at 5,800 rpm from a 340ci motor. The 602 hp at 7,000 was expected. Sure, maybe the engine fell a little short of the 2 hp per cubic-inch, but making 1.85 horses per cubic inch is still respectable. Mike knows he can reach his goal with vacuum pumps and other racing goodies, but for now he's content with the results.